As a conventional torsion damper assembly for a torsion vibration absorbing device, JP09(1997)-229138A2 discloses a torsion damper assembly for a torsional vibration absorbing device. This torsion damper assembly includes a torsion damper idly inside a coil spring disposed between a drive plate connected to a driving power source and a driven plate connected to a driven side such as a transmission. The torsion damper is oriented in a relative rotational direction of the drive plate and the driven plate.
The torsion damper is a cushioning member of approximately cylindrical-shaped and made of an elastic resin material. At least one guiding portion is defined at a major diameter of the torsion damper. A diameter of the guiding portion is designed to be smaller than a minor diameter of the coil spring. That is, there is a predetermined clearance defined between the guiding portion of the torsion damper and an inner side of the coil spring. Therefore, a smooth elastic movement of the coil spring can be allowed.
Further, a diameter of an axially intermediate portion of the torsion damper is designed to be smaller than a diameter of each axially end portion thereof. Therefore, even if the torsion damper is compressed and deformed, the deformed portion of the torsion damper can be prevented from becoming in contact with the coil spring.
However, according to the above-described torsion damper, the diameter of the axially intermediate portion of the torsion damper is designed to be smaller than the diameter of each axially end portion thereof. Further, the guiding portion is defined at the both ends of the torsion damper. Therefore, certain improvements seem to be still expected in assuring a necessary elastic force and a necessary axial length of the guiding portion.
The above-described torsion vibration absorbing device such as a flywheel damper disc and a clutch damper disc has been required to have a high response to a high torque characteristic. In this case, a relative rotational angle between the drive plate and the driven plate is increased. Therefore, the torsion damper is hence required to have a shorter axial length. Further, the coil spring of a damping mechanism is hence required to have a large winding pitch. A coil spring, of which spring characteristic varies in response to a compression amount, can be generally an inequality pitch coil spring. This type of coil spring may have a portion of which winding pitch is excessively large. In this case, as illustrated in FIG. 8, when a coil spring 10 has not been compressed yet, an end portion of a torsion damper 110 may drop or sink into a winding pitch, i.e., into a distance between adjacent winding portions of the coil spring 10.
A need exists for providing an improved damper disc assembly which is provided with a torsion damper that can be prevented from an unnecessary contact with an expanded or contracted coil spring